Portable stroboscopic device for checking electric meters



G. E. MAILLAT March 20, 1945.

PORTABLE STROBOSCOPIC DEVICE FOR CHECKING ELECTRIC METERS Filed May 29, 1941 s Sheets-Shut 1 11/ II IIIIIIIIIIIIIIIIIII I1 Marh 20,1945. 5, MA|| AT 2,371,904

' PORTABLE STROBOSCOPIC DEVICE Fo CHECKING ELECTRIC METERS Filed May 29, 1941 5 Sheets-Sheet 2 March 20, 1945.

G. E. MAILLAT PORTABLE STROBOSCOPIC DEVICE FOR CHECKING ELECTRIC METERS Filed May 29, 1941 3 Sheets-Sheet 3 Patented Mar. 20, l945 PORTABLE STROBOSCOPIC DEVICE FOR CHECKING ELECTRIC METERS Gustave Ernest Maillot, Volslnsde-Bretonneux par Trappea, France; vested in the Alien Property Custodian Application May 29, 1941, Serial No.

France June 9, 1989 7 Claims. (Cl. 175-183) In Patent 2,123,115, the author of the present invention has described a stroboscopic device adapted for the adjustment of subscribers electric meters at the subscribers" premises. This apparatus consists in a case which is fixed, for the adjusting operation, under the meter to be checked. The case contains a standard meter which, with a source of light andan optical system, produces the stroboscopic illumination of the subscribers meter, together with electrical circuits necessary for the comparison of the two meters. These circuits lead to contact plugs or studs carried by the case, which are brought into contact, upon performing the adjusting operation, with othercontact pieces arranged on a panel permanently fixed below the meters to be checked and to which the case is fixed temporarily for performing the operation.

Inthe embodiments described in this patent, the comparison circuits contained in the case were established for permitting a precise adjustment of the meters under all loads as well as under various power factors. This led to a comparativelyheavy and too cumbersome apparatus for the mereuse as a checking appa-' ratus.

The present invention concerns an alternative embodiment of this portable stroboscopic device, designed with the view of permitting'a monthly check of the correct adjustment of the standardised subscribers meters on low voltage means (for instance 110 volts mains) by the sta'fi employed for taking periodically the meters readings. For this purpose, it is necessary to provide a portable apparatus which is much lighter and less cumbersome than that provided. in the cited patent, and which will further considerably reduce the time required for efiecting a checks, while demanding from the operator no special technical instruction.

The device according to the present invention is characterised by the fact that the electric checking Darts consist onone hand in a small number of resistances .which maybe inserted .into the circuit of the current coils of the two meters and which correspond to the usual loads of the meter to be checked, and, on the other hand, in means for .obtaining rapidly, during the comparing operation, the speeds of the standard meter corresponding to the upper and lower permissible limits (for instance 3% and -3%) of the misadjustment.

According to another characteristic of the invention, which is a consequence of the first,

permanently below the meters to be checked and are connected to the checking parts of the stroboscopic apparatus, is constituted by the subscriber's main two-pole switch.

By way of example one has described below and represented schematically on the annexed drawings one embodiment of the device according to the present addition.

Figure 1 is a perspective view of the-apparatus in the operating position,

Figure 2 shows the stroboscopic apparatus in vertical section,

Figures 3 and 4 represent the wiring connections of the checking apparatus and the meter to be verified,

Figures 5 and 6 are, in plan view and transverse section respectively, a subscriber's twopole switch adapted for receiving the stroboscopic apparatus,

Figure '7 is a diagram for the supply of the lamp contained in the apparatus, and

Figures 8 and 9 show schematically two different optical devices giving the required beam of light.

Similarly to the device according to the preceding invention, the device of the present invention comprises a portable case I provided with handles 2, 2' and containing a standard meter 3, a source of light 4 projecting a beam of light through a fixed comb 5, preferably constituted by a film carrying a picture of asystem of teeth, and a. second similar film 6, fixed to the edge of the disc I of the standard meter.

This beam of light is projected through a window 8 in the label plate ll of the meter to be checked and thence onto the lower face of the meter disc which carries marking lines. The case I is fixed, for effecting the check, below the meter 8 to. be checked, by means of contact plugs or studs l3, It, It, It (Figures 2 to 4) fixedto the case I,

' to which are connected the standard meter and the various checking parts and which come into contact with corresponding parts arranged on a panel fixed permanently below the meter -8.

The displacement of the marking lines of the,

disc of meter 8 is observed by reflection in the magnifying mirror l2 provided on the case I, or

by means ,of any other suitable optical device the panel carrying the contacts which are fixed 55.

such as a, rectangular lenses.

As shown in the wiring diagram of Figure 3, the case I comprises, apart from the optical system, thecurrent. and voltagewindings l1 and [8 of the standard meter, a high resistance 35 and a number of, for instance three other resistances prism fitted with convex and is, while the current jaws a'handle I1, is

, serving the purpose oi further provided with four contact pieces of apertures ll, ll, m w. nals oi the standard meter 20, 20', 2|" actuated from knobs 2|, 2|, 2|" (Figure case I. ventilated in order-notto harm, by radiation of heat into the case I, the precision oi! the standard meter. To this effect, the resistances are arranged in a list apertured box 22 (Figural) dried to one side of the case I without contact with the latter. in order to leave an interval which will protect the case against any undue heating. Besides, the switches 20, 20', 2|" with an automatic openingdevice in case of excessive heating,-comprising for instance bi-metai strips. These resistances are chosen in a manner to correspond. according as to whether there is only one or a certain number of them connected in parallel, to certain usual loads of the subscriber's meter, as tor medium load and full load.

The windings oi" the standard meter are conthe outside by push 1) provided on the nected. as indicated above, to four plugs or studs II, I4, II, II provided on the case I and correspond to a set of similar contact pieces II, ll,

IV, II constituting the tour studs of the subscriber's main two-pole switch 23 (Figure 4) which connects the meter 8 in the usual manner to the subscriber's inside installation as comprising for instance lamps 2t, 25' or other utilities. It will be seen that when the contacts II-IS', Il-Il', IS-Il', Ii-Ii' are established by the application of case in the operating position, the II, It on the mains 28 by 21, 2!, II, II and 28, I1, 29, I1, W-ll, 38, II, It-IS', It, 3|, 8|

voltage windings connected in series with one, two resistances II, It, it""(in parallel) (circuit 21, is, 11', llf-ll, II, It, 20", It" for instance. Il-Ii', I8, II, It, 20), this resistance It" for instance being connected in paraliel'to the subscriber's circuit, so that the checking may be etiected without disturbing-the latter. It will be s'eenthat it is owing to the arrangement adopted for the electric checking connections that itis possible to connect the apparatus to the subscrib'ers main two-pole switch.

It" which may each be connected sepa-' or two or three in parallel, to the termiby means of switches may be provided 7 instances low load. a

I, with the switch I:

These resistances are heat-insulated or will iii: the checking apparatus two-pole switch 23 2', then insert it in the-subscribers load circuit At this inornent,

menace;

not protrude over the 11s 5|: and the contact pieces of the case penetrate into the latter. In the embodiment provided by the present invention, the checking or. the misa'diustment oi the meter under check (with its sign or is effected by varying the meter from sible misadjustment, by means of a switch 31. supplying its voltage coil throughone or the other of two toppings,- the lower limit of the other to the upper limit. being, for instance, adjusted to the predetermined upper limit of inaccuracy (3% fast) while the lower limit (3% slow) is given by the other position of switch 33, the operator will proceed as follows. Holding the case I in one hand, he

misadiustment, and the by holding the apparatusior instance with his two hands by the handles 2,

by opening said switch it it is not already opened.

the lamp of the optical system will light up and the standard meter will rotate;

iii) oi both meters are connected in'parallei andbywindings Il-I'I' are.

or three of the The operator'will merely have to observe in the magnifying glass I2 the image of the marks carried by the disc of the subscriber's-meter under check. and then, by actuating in succession-the corresponding push-knobs, insert in the circuit any one or combination of the said resistances to give the usualloads, and check, by actuating the switch 33, ii the speed of the subscribers meter'is comprised between the two limiting values of the standard meter.

The arrangement of the stroboscopic apparatus and the rapid method of verification employed 'permit .the use of resistances of the type generally employed in electric irons, for the resistances IS, 19, lsf'servi'ng as test loadings for the meters. Thus-leach resistance will consist for instance in a resistant strip, about 5 feet long, wound on a mica sheet inserted between two other insulating mica sheets somewhat larger than the first, the latter sheets being held be tween two aluminium plate riveted to one-anotherand giving the assembly the required mechanicalprotection. Resistances of this type 7 To this end, the subscriber's main two-pole switch (Figures 5 and 6); which compri as usual a base plate ",an insulating lid ll, tour l2, 2'- and' 53, I3 and two blades 54,14 and II, II mounted on an axis 8' actuated by further provided with iourpins the insulating lid II and fixing the case I to the pieces against which will come to lie the four contact pieces of case I ior instance in the form of brass "springs, blades r.

the stroboscope caseare conthe posts I, ll, II, II carry ti utedy plu can (Figured) in a manner to .i'orm sockets for the or brushes. In case thesaid plugs. .The top oi-posts ll, 0|, 6|, I may or coursealso with the result are here 'very advantageous by reason by their very low weight; they haveup to the present generally been used for giving a rapid and strong heating, which might here seem to prove harm-" i'ui. Their use for the present purpose is possible here only because of the fact that the time required for performing a sttoboscopic measurement; i. e., the time during which the resistances are actually in circuit,is very short, say about. Y

10- seconds. The amount of heat to be dissipated is consequently very small andj it will therefore sui'iice, in practice, to arrangethese test resist-' T ances II, It, It", as shownin Figure 1, in an apertured casing 22 fixed to the stroboscope being separated from one anniher by a small interval of air oi about it c Apart from the stroboscopic checks indicated above, it will also be'required to check the meter for correct starting under very low load con ditions. v Y Accordingly switch ll. (see P18. 3) may be closed when the subscriber's main switch is open that a resistance 38 is connected in the. current circuit of the meter being Resistance 86 corresponds, for example, to 34 of the rated load, which is. illustratively, the minimum startingload. I

speedoi the standard L one to the other limit 'oi the permis-.

one of them corresponding to The meter of the device to the subscriber's standardmeter.

.With the main switch 23 open andswitch II of the case also open, the circuit will then be the following: 28, 21, 29, n', n, w, u, 11, ll, a,

The lamp of the stroboscope device could be supplied by battery arranged in the case, but,

with the same view of decreasing the weight of the apparatus, which is an essential condition for making it practical in use, it is p'reierableto supply the lamp directly from the A. C. mains. The fact that the stroboscopic device is placed immediately below the meter under check, at a small distance from the latter, and that the disc of the latter, especially its lower face, which receives the stroboscopic interrupted luminous flux, is placed in nearly complete darkness, permits the use of a very weak source of light,for instance the bulb of a pocket lamp, consuming 0.5 amp. under. 3.5 volts. Such a lamp will pro- (1 w 1 not disturb in any way the precisionof the There are various arrangements for supplying such a lamp from the mains, as especially a transformer, but the comparatively large weight of the latter would make the case unnecessarily heavy. a condition which it is absolutely necessary-to avoid in this case. A resistance could also serve the purpose, but it would heat the case, and such heating is to be avoided, and further consume a comparatively large current.

According to one characteristic of the present invention, one will preferably use, for supplying this lamp 4 (Figure '7) .a condenser 35 connected in series with the lamp. which will thus operate on the charging and discharging current of the condenser. An adjustable resistance 31, in parallel with the lamp, permits the adjustment of the lamp voltage.

Owing to the low value of the illumination, it is necessary to take special precautions in order to obtain a suilici'ently sharp stroboscopic effect,

i. e., sufficiently sharp cuts of the luminous flux, especially if the disc of the standard meter pro.- ducing these cuts rotates very slowly .under weak loads. Thus, for instance, an 8 to 10 cm. diameter disc may carry, around its periphery, 1000 lines, i. e., about 30 lines per cm. periphery. According to the citedpatent, the luminous flux passes in succession through a fixed comb and the teeth of the rotating disc of the standard meter. Such a device, however, cannot give com plete cccultations, even if the comb anddisc are very close to one another, because, owing to the dimensions, which are not negligible here, oi'the source of light, there will always pass a certain amount of" diffuse light, which will be suflicient for decreasing to a large extent the stroboscopic efiect. Forremedylng this drawback, the comb teeth and the teeth on the disc of the standard meter are made, according to the present invention, as the author has already indicated previously, by means of a circular film carrying, at the required scale, a photographic copy.- as line and e practically no heating in the caseand thusschematically in Figure 8, which is an elevational view of this part of the apparatus.

The film carrying the photographed teeth I and constituting the fixed comb is illuminated from below by the lamp II by means of the collimator 42. Its image is formed by a lens 63 upon the photographed teeth-carying film 44 forming.

the edge of the disc of the standard meter, this image having exactly the same dimensions as the film teeth 44. I Thus, when the movable teeth or scale 44 comes to lie in a position in which its sharp as it is desired, of teeth or simply of a scale, at first drawn at a larger scale, and the image of the hired comb is then projected upon the film forming the teeth on the disc-of the standard meter. In this way, the fixed teeth (image) and the moving teeth (object) liein the "same plane and the interruptions of the beam are consequently perfect. This device is shown mator 41.

slots areopposite the teeth of the image, the luminous flux will be completely interrupted and the stroboscopic effect excellent.

In certain cases, it may be suflicient to use a simplified projection device. The image of the photographed teeth-carrying film forming the edge of the disc of the standard meter is then projected at an enlarged scale by the optical system under the disc of the meter under check. This film 45 (Figure 9) is .illuminated from below by a lamp 66 which may be provided with a colli- An optical system 48 projects the image of this film 45 underthe disc 49 of the meter under check. There will thus be formed,

beneath the lower face of the disc of the meter under check, a region illuminated intermittently with'a frequency equal, to the travel" frequencybf the lines or teeth of the disc of the standard nieter in the luminous beam.

What we claim is':' Y 1. Stroboscopic device for checking," tric meters of low voltage mains" subs comprising a graduation provided onfthe' 'dge of the lower face of the disc of the meter tofbe checked, 2. portable case containinga'source-jot light, an optical projection system projecting" a beam of light upon the lower, divided face of the disc of the meter to be checked,'a standard meter with its disc provided on its edge with means for periodically interrupting the beam of light projected by said optical system, electriccomparison members consisting of a'small number Of individual resistance units corresponding to a certain number of usual loads of the meter, and means including individual switch units as sociated respectively with each of said individual resistancaunits for connecting these individual resistance units in series with the current winding of said standard meter, contact pieces arranged on the case and to which are connected the windingsof the standard meter, a panel fixed below the meter to be checked and provided with contact pieces connected to the .windings of the meterto be checked and corresponding to those of the case for connecting the two meters to the distribution mains, and with members for I fixing said case'to the meter to be checked, means in this case for causing the standard meter to rotate, during the check, at the speeds corresponding to the upper and lower permissible values of inaccuracy, these means comprising two tappings on the voltage winding of the stand- .ard meter and a switch for connecting one of these tappings to the mains.

2. Stroboscopic device for checking the elec-.

means including individual switch units assothe speed corresponding exactly to the load under test. I

i with its disc provided on its edge with means a for periodically interrupting the beam of light projected by said optical system, electric comparison members consisting of a small number of of usual loads 01' the meter, and means for connecting these resistances in series with thecurpole connected spectively connected to ter and correspondingto the four contact pieces of the case for connecting the two meters to the- I. malns,.-members arranged on the switch for fix- 'scribers-circuit, arranged below the meter tobe i checked and comprisinga base plate and an in- .sulating lid provided with four apertures, memiected by said optical system, electric compari- 'son'members consisting oia small number of individual resistance units corresponding" to a certain number of usual loads'oi the meter, and

ciatedrespectively with each of said individual resistance units for connecting these-individual resistance units in series with the. current windlug of said standard meter, contact pieces arranged on the case and to which are connected the windings of the standard meter, a panel fixed below the meter to be checked and provided with contact pieces connected to the windings of the meter to be checked and corresponding to those i' or the case for connecting the two meters to the I distribution mains, and with members for fixing said case to the meter to be checked, two tapp gs on the ,voltage winding of the standard meter. corresponding tospeeds 3% above and 3% below 3. Stroboscopic device for checking the electric meters of low voltage mains subscribers, comprising a graduation provided on the edge of the lower face of the disc of the meter to be checked, a portable case containing a source of light, an optical projection system projecting a beam of light upon the lower, divided face of the disc of the meter to be checked, a standard meresistances corresponding-to a certain number rent winding of the latter, four contact piecesairanged onthe case and to which are connected the windings oi the standard meter, a main'twoto the subscriber's circuit and arranged below the meter to be checked, rour contact pieces arranged on this switch, rethe terminals of the lating the case, means provided in the -latter for causing the standard meter to rotate, during the check-attire speeds corresponding to the upper and lower permissible values of inaccuracy. 4. Stroboscopic device for checking the ,elec tric meters oi lowvoltage mains subscribers,

"comprising a graduation provided on the edge of-the lower face of the disc orthe meter to be comparison members consisting of a small number of resistances corresponding to a certain number of usual loads of the meter, and means for connecting these resistances in series with the current winding of the latter, romcontact,

pieces arranged on'the case and. to which are connected the windings of the standard meter,

a .main two-pole. switch connected to the sub through the said apertures, means for connecting these :[our posts to the four terminals or the switch respectively, contact pieces carried. by

these posts and corresponding to those of the case for connecting the two meters to the mains when the case is fixed to the lid of the switch.- a

- means in this case for causingthe standard meter to rotate, during the check, at the speeds corresponding to the upper and lower permissible values of inaccuracy. 5. Stroboscopic device for checking the electric meters of low voltage mains subscribers, comprising a graduation provided on the edge or the lower face of the disc or the meter to be checked, a portable case containing a source of light, an optical projection system projectinga beam of lightupon the lower, divided iace of the discof the meter to be checked, a standard meter with its disc provided on its edge with means for periodically interrupting the beam oi light projected by-said optical system, electric comparison members consisting of a small number 01 resistances corresponding to a certain number of usual loads of the meter, and means for conneoting these resistances in series with the current winding of the latter, contact pieces arranged on the caseand to which are connected the windings of the standard meter, a panel fixed below the meter to be checked and provided with contact pieces connected to the windings of the meter to be checked and corresponding to those of the case for connecting the two meters to the distribution mains, and with members for fixing said; case to the-meter to be checked, means" in this case for causing the standard meter to rotate, during the check, at the speeds correspond-.

ing to the upper and lower permissible values (of inaccuracy, a high r sistance arranged in the case for checking the correct starting upof the meter under check, and. means for connecting this high resistance in series with the current windings of the meter under check and or the 4 standard meter.

- 6. Stroboscopic device for checking the eleccomprising a graduation provided on the edge of the lower face of the disc of the meter to be checked, a portable case containing a source or light consisting in a very low voltage and low the beameotlight projected-by said optical sys 'tem, electric comparison members consisting or i a small number of resistances corresponding to acertain number of usual loads of the meter,

and means for connecting these resistances in series with the current winding of the latter, contact pieces arrangedon the case and to which are connected the windin'gsoi the standard meter, a panel fixed below the meter to be checked i an provided withcoutact pieces connected to .the two meters to the distribution. mains, and

sp eds trio meters of low voltage mains subscribers.

powered electric lamp connected to the supply windings of the meter to be checked and qcorrespondingto those of the casefor connecting .7

Iwithmembers for fixing said case to the meter 1 tube checkedpmeans in this case [for'causing the.

- standardmeterto rotate, during. the check, at: corresponding to the upper and lowerf o! the switch and. protruding from the 116.75 permissible valiles-otinaccuracy;

tric meters of low voltage mains subscribers,

" comprising a graduation provided on the edge of the beam of light between the source of light and the disc of thestandard meter, an optical system arranged between the fixed screen and the disc of the standard meter for projecting,

in the plane of the teeth of the disc, an image of the teeth of the fixed screen onto the disc of the meter to be checked. electric comparison circuits, means for connecting these circuits to the windings of the standard meter, contact pieces arranged on the case and to which are connected the windings oi' the standard meter and the comparison circuits, a panel fixed below the meter to be checked andprovided with members for fixing the case and with contact pieces connected to the windings of the meter to be checked and corresponding to those of the case for connecting both meters to the supply mains, and means for varying the speed of the standardvmeter.

GUBTAVE ERNEST MAILLAT. 

